The entrance to the bunker is via simple concrete stairs, dug into the gardens of the east wing of the Hôtel de Montmorin, the current Overseas Ministry in Paris (7th).
At the bottom of the steps, a first rusty door leads to a huge technical room that serves as a storage place.
By passing several corridors surrounded by pipes, access to the underground shelter finally begins, in front of this imposing watertight door, decked out with a porthole and which is operated with a wheel.
"Welcome to the submarine," says Aurégane Binard, member of the ministry's cabinet, who begins a guided tour of the premises for us.
Behind 1m30 thick walls, with greenish and faded roughcast, the "hidden" bunker of the Ministry of Overseas Territories ensured absolute sealing of the premises.
"It was built in 1937 in a context of fear of gas attacks, as we experienced during the Great War", recalls our guide of the day.
The objective of the bunker, like most of those dug at that time under different places of power in Paris, was above all to organize the passive defense of the country by ensuring the continuity of the administration in the event of attacks. on gas.
Offices, rest rooms, toilets, access to water via a well drilled 60 m deep… Everything was planned to accommodate at least 250 people in an emergency for 15 days.
Built on two levels, the hermetic bunker also had to have the capacity to generate its own electricity in the event of power cuts.
In the engine room, four bicycles connected to a battery of pipes could produce energy by pedalling.
And also allow to renew the air by a pump system evacuating the CO2.
Watch our video report at the top of the article.